(1) Field of the Invention
The present invention relates to a method for the treatment of fibrous materials. More particularly, the present invention relates to a method for the treatment of fibrous materials for imparting a durable flame retardancy to a fibrous material composed of a cellulose fiber or a mixture of a cellulose fiber and other fibers.
(2) Description of the Related Art
As the conventional means for imparting a durable flame retardancy to a fibrous material composed solely of a cellulose fiber, there can be mentioned a Proban method (Albright & Willson Co.) in which the fibrous material is ammonia-cured with a tetrakishydroxymethyl sulfonium salt-urea precondensate, a method in which the fibrous material is treated by heat-reacting N-hydroxymethyl-3-dimethylphosphonopropionamide (Pyorovatex CP supplied by Ciba-Geigy) with a methylolmelamine type compound, and a method in which the fibrous material is treated by polymerizing a vinyl phosphonate oligomer (Fyrol 76 supplied by Stauffer Chemical Co.) and N-methylolacrylamide in the presence of a catalyst.
As the conventional means for imparting a durable flame retardancy to a fibrous material composed of a polyester fiber, there can be mentioned an exhaustion bath method in which hexabromocyclododecane is absorbed in the fibrous material by using an aqueous dispersion thereof, a method in which hexabromocyclododecane is diffused in the interior of the fiber according to the thermosol process, an exhaustion bath method using a dispersion of tris-dichloropropyl phosphate, a method in which tris-dichloropropyl phosphate is fixed to the fibrous material according to the thermosol process, and a method in which a phosphorus-containing cyclic compound is fixed to the fibrous material according to the thermosol process using an aqueous solution thereof.
These flame-proofing methods are effective for fibers composed solely of a cellulose or polyester, but are not effective for a mixed fibrous material of a polyester fiber and a cellulose fiber. Especially in the case of a fiberous material comprising a polyester fiber and a cellulose fiber at a mixing ratio of from 70/30 to 30/70, it is difficult to obtain a product having a practically satisfactory flame retardancy, touch, and physical properties.
As a method for imparting a flame retardancy to a fibrous material composed of a mixture of a polyester fiber and cotton, there is known a method in which hexabromocyclododecane, antimony trioxide and an acrylic latex are used in combination. However, this method is defective in that the touch of the processed product is hard and the hue of the dyed product is whitened.
Moreover, a method is proposed in which a fiber is impregnated with a composition comprising a tetrakishydroxymethyl sulfonium salt-ammonia condensate (THPN), methylolmelamine and urea, dried and heat-cured [American Dyestuff Reporter 74, No. 1, 35-40 (1985)]. The treated product obtained according to this method has a relatively high flame retardancy, but the method is defective in that the given flame retardancy cannot resist a 50-times repetition of washing, which is ordinarily required in the field of clothing, and the hardening of the touch is extreme.
It is considered that it is difficult to impart a durable flame retardancy to a fibrous material composed of a mixture of a polyester fiber and a cellulose fiber because, in the polyester fiber, the flame retardancy is exerted by a promotion of melting while the flame retardancy is exerted by a promotion of carbonization in the cellulose fiber, fusion falling of the polyester is inhibited in the presence of the cellulose because of this difference of the combustion behavior, and thus the self-extinguishing property is reduced.